Method of producing polyvinyl chloride fibers having improved thermal properties



May 11, 1965 JIRO SHIMEHA EI'AL METHOD OF PRODUCING POLYVINYL CHLORIDEFIBERS .HAVING IHPROVBD' THERHAL PROPERTIES l'iIOd IlI'Oh 29, 1960 TIMEv $1 m .P m

in 3 55 mmuzfiim Patented May 11, I965 3,183,201 METHOD OF PRODUCINGPOLYVINYL CHLO- RIDE FIBERS HAVING IMPROVED THERMAL PROPERTIES r JiroShimeha, Shuii Ozawa, Ikuzo Tanaka, Shumchr Matsumura and HiroakiKubota, all of Iwakuni-shi, Yamathose of polymers of vinyl chloridepolymerized at a guchi-ken, Japan, assignors to Teikoku Jinzo KenshiKabnshiki Kaisha, Nishi-ku, Osaka, Japan, a corporation of Japan FiledMar. 29, 1960, Ser. No. 18,280

Mar. 31, 1959,

Claims riority application Japan 35; Apl'. zz, 1959, 34/12,941; Sept. 3,1959,

34/27,976, fa l/27,977; Sept. 25, 19 59 34/30,.678r0ct.

29, 1959, 34/34,1'54 v v 9 Claims. (Cl. 260-312) This invention relatesto a method of producing polyvinyl chloride fibers having improvedthermal properties. More particularlythe invention relates to a methodof producing on an industrial. scale synthetic fibers having highdimensional stability from either highly crystalline polyvinyl chloridesor copolymers containing more than 90 mol percent of vinyl chlorideunits. i

Hereinafter, the polyvinyl chloride and the copolymers containing morethan 90 mol percent of vinyl chloride unitsand .vinyl or otherunsaturated compounds will be referred to asvinyl chloride polymers.

An object of this invention is to provide a method of producing on anindustiral scale fibers having high dimensional stability from vinylchloride polymers.

Another object of the invention is to provide criteria of selectingvinyl chloride polymers suitable for spinning and manufacturing on anindustrial scale into fibers possessed of high dimensional stability.

A still further object of the invention is to provide an -.industrialmethod of preparing a spinning solution by dissolving vinylchloridepolymers having comparatively high crystallinity.

A further object of the invention is to provide a method of preparingfirst a stable'slurry of swollen vinyl chloride polymers in order torender easy the handling of said I vinyl chloride polymers in preparingthe solution thereof from those vinyl chloride polymers possessingcomparatively high crystallinity.

A still further object of the inventionis to provide criteria ofselecting solvents suitable for preparing the aforesaid stable slurry;

A yet another object of the invention is to provide a method ofdissolving the aforesaid slurry and methods of drawing and heat settingthe fibers obtained-from the vinyl chloride polymers possessingcomparatively high crystallinity.

Other objects of; the invention will become apparent 2 1322 (1958) andBelgium Patent No. $69,632]. It is also known that the articles formedof these highly crystalline polymers of vinyl chloride, when comparedwith higher temperature, manifest a conspicuous enhancement in theirdimensional stability as well as mechanical properties especially at ahigher temperature, for example, such as tenacity, elasticity, modulusand hardness.

On the other hand, despite the fact that excellent propf erties ashereinabove described are possessed by these articles formed of polymersof vinyl chloride polymerized at a lower temperature, on account of thelowering in their solubility and formability, it is very difiicult inthe first place to prepare the spinning solution on an industrial scaleby dissolving these vinyl chloride polymers as in the conventional dryspinning and wet spinning proc- Infact, the existing state of ail'airsis such that I esses. there has been practically no literature to datereporting in detail any way of producing fibers from polymers of vinylchloride polymerized at low temperatures.

In order to produce on an industrial scale fibers of vinyl chloridepolymers improved in their thermal properties we found that by carryingout the following stepsv it was very effective. In the first place,vinyl chloride polymers having an average degree of polymerization andfalling within a specified range as to their degree of crystallinitywereused. Then, instead of instantly dissolvingthese polymers in thesolvent used, a stable slurry of said polymers'and the solvent wasprepared.- Operations such as transporting this slurry, etc. wereperformed while in this slurry state, and then the slurry was dissolvedin as short a time as possible, followed immediately by performing thespinning sothat thev time in which the polymer remains in the dissolvedstate was reduced to as short a time as possible. Thus, we found that itwas possible to produce on an industrial scale fibers from thehereinabove described vinyl chloride polymers obtained by polymerizationat a low temperature. For sake of simplicity, the invention will bedescribed with respect to pure polyvinyl chloride. First, an explanationwill be made of the characteristics required of the vinyl chloridepolymers to be in this invention.

As already described hereinabove, it is necessary that the startingmaterial for obtaining the fibers from vinyl chloride polymer improvedin their thermal properties be highly crystalline polymers. Whileheretofore many attempts have been made for determining the degree ofcrystallinity of polyvinyl chloride, none have been standardized.

Lately, according to Mizushirna et a1. (Lecture at the I Conference onHigh Polymers at Osaka, Japan, Septem ber 1958), it has been discoveredthat with respect to the infrared absorption spectra of vinyl chloridepolymers, the absorption at 1426 cm." is caused by the bending motion of-CH -group in the crystalline part and the absorption at 1434 cm.- iscaused by the bending of v.

--CH -group in the amorphous part of the polymer.

Following the reports of the aforesaid Mizushima et a1., we madecomparisons of the ratio, D1426/D1434, of the optical densities at 1426cm. to 1434 cm.- of the infrared absorption of the several kinds ofvinyl chloride polymers with the properties of the respective fibersobtained from these polymers. The data are shown in in case of'SampleNo. 6 of Table I, when the dissolving Table I. of 10 parts of polyvinylchloride whose D/D=l.293

TABLE I Polymerization Properties oi polymers Properties of fibersSample No. I

Temp. SP. (1. Density 8 Tenacity Extensi- 0.) Catalyst I Medium P D/D(ems/gr.) (cmJ/gr.) (percent) (gr./den.) bility v (percent) 55 '.B.P.OWater 1,430 1.015. 0.47 1. 398 32.8 3.2 21.3 20 B0311); Monomer. 1,1801.192 0.16 1.410 11.8 1.4 14.1 2, 500 '1. 177 0.11 1. 409 8. 3 3. l 14.6 i E l, 200 l. 321 0.13 1. 413 9. 7 3. 5 14. 1 t) 1,260 1.260 0.131.414 0.6 1.8 12.0

1, 210 1. 188 0. 17 '1. 413 17. 2. 7 19. 9 980 1.193 0.24 1.412 14.4 2.822.3 1. 510 1. 226 0. l8 1. 417 11.0 2. 3 17. 6 1, 040 1. 231 0.20 1.416 7.1 2. 3 16.4 1, 190 1. 105 0. 13 1. 416 18. 4. 1 l5. 1 1,370 1.1060.10 1.402 27.9 3.8 19.6 1, 720 1. 114 0.16 1.401 26. l 3. 0 18. 4 1,190 1. 118 0. 15 1. 410 18. 7 2. 8 24. 6

y peroxide- B(Bll)e-Boron tributyl. d S G.-Apparent specific gravitymeasured by means of. U fl y gefl JIS- 6721(55), so-called bulk densitgin gr./cm.' ductant. Rs-(Co-napthenate-HrOn)reductant. e S-Percentageshrinkage of the fl rous samples when iml -Average degree ofpolymerization (viscometrie- D/D-Dl 26/D1434. The D/D-vaiue-is detepedas the optical density ratio of infrared absorption by samplepolymers at 1426 cm: to 1434 cm.- where the percentage transmittance at1530 cm: is above 80 and the percentage transmittances at both-1426 cmand 1434 cm.- are between 15-50. The test pieces of sample polymers areshaped by compressing the powdery mixture of polymer and KBr. Althoughwhen the solvent extraction, repreeipitation, and heatin are rformedwith respect to identical-materials, these va ues c ange somewhat, sincein case of sufficiently refined samples a precision of =0.01 can beattained it was found that these values couldreasonably be considered asbeing indications of the inherent characteristics oi! the material.

In this invention, the" ratio D1426/Dl434, of the optical densityat,1426 emf, D1426, tothe optical density at 1434 cmf D1434, of theinfrared absorption of the vinyl chloride polymers will be abbreviatedas "D /D" for sake of simplicity.

Table I shows that,- the larger the D/D values possessed by the materialpolymers, the greater was the improvement attained in the thermalproperty of the fibers obtained from them, independently of the type ofpolymerization, with the exception of the temperature at which thepolymerization was' carried out. In other words, it

reveals that the lower the temperature at which the polymers werepolymerized, the larger the D/D values the polymers would have. When theD/ D value of the commercially available polyvinyl chloride obtained bythe conventional high temperature polymerization method was sought afterhaving purified them by rinsing in methanol for 2 hours at 60 C. anddried, results as shown in Table H were obtained, in which it was shownthat the D/D values'of the commercially available polyvinyl chlorideobtain'edby the high temperature polymerization method were in all casesbelow 1.08. Thus it was confirmed that their D/D' values were withoutexception smaller than that of the polyvinyl chloride obtained by thelow temperature polymerization method.

See footnote oi Table I.

From the aforesaid reasons, although it has become apparent that it waspossible to obtain fibers having substantially high dimensionalstability if polymers having comparatively high D/D values are used, forexample,

mersed in boilingiwater for 5 minutes-Conditions for preparation offibrous samples 10 parts of the polymer were dissolved into parts ofcyclohexanone while heating, and then spun into methanol by wet spinningat ordinary temperatures. Drafting ratio on spinning: 1.0-1.5. Windupspeed 1-5 m./mln. After rinsing the fiber obtained in methanol for 3-7days, it was drawn in a glycerlne bath at a temperature of C. with adrawing ratio of 4-40 times, and thereafter while using the sametemperature, it was heat set atl cotnstant length (so called set atstretch") for 10 in nu es.

(degree of polymerization:4,000) in 90 parts of cyclohexanone wasattempted at about 90 C., the dissolving was not possible. On the otherhand, in case of the polyvinyl chloride of Sample No. 1 whose D/D=1.015(degree of. polymerization 1430), the percent-shrinkage in boiling waterof its fiber was 32.8 and it can be seen that its dimensional stabilitywas very poor.

In the above manner, we investigated the thermal properties of thefibers from vinyl chloride polymers of various D/D-values. As a result,we found that fibers from the vinyl chloride polymers specified by D/D-values of more than 1.08 were superior in their thermal properties tothose obtained by the conventional high temperature polymerizationmethod. However, in the caseof those vinyl chloride polymers specifiedby D/D l.27, on account of their being less soluble in the solvents,many troubles have occurred in processing them. Consequently, in thisinvention we arrived at the conclusion that it was necessary to use inthe first place the vinyl chloride polymers specified by the D/D-valuesranging between 1.08 and 1.27.

While we have found that the use of vinyl chloride polymers specified bythe D/D-values ranging between 1.08 and 1.27 was one of the necessaryconditions to make the processes of both dissolving and spinning easy,as well as to form fibers having high dimensional stability, it was alsofound that a very close inter-relationship existed between the degree ofpolymerization of the vinyl chloride polymers and the solubility of thepolymers as well as their ability of fiber formation. As a result ofhaving made various investigations into the relationship between thedegree of polymerization of the vinyl chloride polymers on one hand andtheir solubility and ability of fiber formation on the other, we foundthat, besides the condition requiring the D/D- value of the polymer befrom 1.08 to 1.27, it was an important requisite that the vinyl chloridepolymer whose degree of polymerization is from 500-2500 be selected inorder to render into fibers on an industrial scale polyvinyl chlorideshaving high dimensional stability.

TABLE-III- Temp. Sample sample N o. poly1ner-- P DID Solubility ized at0.)

1 50 ca. 3, 000. 1. 286 Soluble only up to 4.3 weight percent in hotT.H.E. 2 30' ca. 4, 000 l. 241' Insoluble at the cone. of 10 i I weightpercent in hot T.ll.F. 3... -40. ca. 2, 500 l. 264 Soluble at the cone.of 10 weight percent in hot T.H.F. 4 l5 4, 810 1. 147 Insoluble at thecone. of

weight percent in hot T.H.F. 5 -18 3, 760. l. 198' Soluble, but gelationoccurred on cooling. 6- 28 2, 890. 1. 223 Do. 7 -5 620 1.102. Can'bespunirom Anon solution containing. 12 weight percent of polymer. 8 30.450 1. 233 Can be spun from Anon solution eontalnlng'12 weight percentoi polymer, butthe fiberobtainod is brittle. 9 0 420 1, 095 Cannot bespunbecause of occasional break in continuity oi fiber.

T.H.F.Tetrahydroiuran. Anoncyclohexanonel In Table. III, the.interrelation between the degree of polymerization of vinyl chloride.polymers, and their solubility to the solvent and the. ability of fiberformation is shown;

It canbe understood from-theforegoing TableIII that in the caseofavinylcchloride polymerxwhose degree of polymerization'is more than2500, a solution of high concentratiorr=cannot be obtained evenifa goodsolvent is used, while in case of thatwitha' degree of polymerizationless-thanv 500, itsability offiber formation becomes very poor.

Thus,.wefound the necessityof selecting and-using:- vinyl chloride.polymers whose D/D-value .is between 1.08'-1.27 and thedegreeofpolymerization is between 500-2500 in order to obtain. on' an.industrial scale-fibers;

having high dimensional stability.

' The. aforesaidxvinyl chloride polymers having a D/D value ofv1.08-4.27 and degree of polymerization between 500-2500 willbehereinafter referredto, for sake. of

convenience,.as PVC L,.and :themethod of dissolvingthe same in thisinvention will bedcscribed -below.. While we.

have described .hereinabove thattheser PVC-L. are" those that fallwithin thezrangeasto make possibletheoperae tions of suchas dissolving,.spinning, etc. aswell asthe production of fibers it is combined witha.solventin an.

amounta1.0-4 times by weight thereof,.the difliculty lies in the factthat. asolvent which cancompletely dissolve the polymer is not readilyavailable. Even if it were possible. to-accomplish the completesolutionaunder. un-

practical laboratory conditions, -an.accountof theoccurrence-ofgelation'whenwit is kept standing, itis' after all impossible. to obtaindirectly a stable solution. Secondly, inpractically everyinstancewhenPVC-L is mixed with a solvent, the solvent immediately,becomes absorbed by the polymer and does not become'a stable slurrylikemixture whose viscosity changeis smallbut becomes such that thewholemixture exhibits a wetsand-like appearance Thus,manifestingnofluidity at all, itshandling onan industrialscale becomes'very diflicult. Of course, it is: possible to. dissolve thismixtureby'heat- Those. points of less than 0.2 gr./cm.

ing but with gelation easily occuring, it cannot be said i to be astable solution.

While in handling the conventional vinyl chloride polymers both of theaforementioned points-need to be consideredalso, in case of PVC-L, thisis particularly true.

In view of these characteristics, we found that in order to makepossible the production of fibers on an industrial 0 scale from PVC-L,it was necessary to first prepare a stable slurry, of restrictedlyswollen polymer particles with small change in its viscosity by mixingthe polymer with the solvent until'the viscosity of the mixture tends toan equilibrium value and then while maintaining it in this slurry-likestate with small change in its viscosity to carry. out the variousoperations necessary until dissolving, followed by spinning within ashort time while heating and dissolving the mixture. And as a result ofour detailed study of these two aforesaid abnormal characters whichbecome obstacles in practicing the method of this invention while usingPVC-L, we found the three requisites for solving these obstacles andthus were able to arrive at a method for producing on an industrialscale vinyl chloride fibers having superior dimensional stability.

(1) By increasing the apparent specific gravity of the PVC-'L polymers.(2) Bypreparing a stable swollen slurry by the combination of the PVC-Lobtained in (l) with the solvent.

(3) By spinning immediately the slurry obtained in (2) after. heatingand dissolving the same in a short time.

These three methods will be described hereinafter in detaillinthe ordergiven.

(1) Method of increasing 'the apparent specific gravity of the polymerWhcn'we made a further study into the difierencesi in thecharacteristicsof PVC-L and the conventional vinyl chloride polymers in their behaviorswith respect to solvents, we found surprisingly that there wasa great Ydifierence. between the apparent specific gravities of thecific gravityof the polymer particles is subject to change a depending .upon itsformation condition, the bulkiness of the; polymers prepared byprecipitation polymerization, which 18 generally used at present forobtaining PVC-L,.

is very high, the apparent specific gravity being about swollen slurrycan be obtained upon mixing with a solvent, it becameapparent that theapparent specific gravity of the polymer mustbe adjusted so that it is0.3-0.6 gr./cm. In. raising the apparent specific gravity of those.polymers with apparent specific gravities less than 0.2 gr./cm. it ispreferable to use, for example, singly or in combination one or two ormore of the methods j given below. By the use of these methods thespecific apparent gravity can be raised to maximum 0.7 gr./cm.

While .the following three methods have been given, they are merelyintended in an illustrative sense, and the invention should not belimited thereby.

(a) The method of heating the PVC-L at a tempera-l ture in" arange thatis above the temperature at which.

the-thermal motion of the molecule becomes active whereby stabilizationof the fine structure occurs, but

below the point at which discoloration occurs, thermal%,

decomposition, etc. can be avoided.

(b) The method of first adding a mixture of a good v solvent and anon-solvent to the PVC-L and allowing a small quantity of the solvent tobe absorbed therein, and. v I thereafter heat treating this to atemperature within the range as mentioned in subparagraph (a), above.

(c)- The method of adding a small quantity of sol-- vent to thepolymerization system during the polymeri-l zation reaction forobtaining PVCL, and after separating.

However, in order that a stable 5 the polymers from the polymerizationsystem, heat treating the same within the temperature range as mentionedin subparagraph (a), above.

Now, if the method of adjusting the apparent specific .gravity isdescribed in further detail, it is as follows:

(a) The temperature at which the thermal motion of the molecules becomesactive is 70-80" C., which temperature is generally referred to as thesoftening point. At a temperature higher than this, on account of thesoftening of the polymer, stabilization of the structure occurs. On theother hand, while the temperature at which discoloration and thermaldecomposition can be avoided is in case of polyvinyl chloride generallyat below 150 C., by adding a stabilizer as shown in subparagraphs (b)and (c), below, it is also possible to raise this temperature greatly.Since these temperatures at which the motion of the molecules becomesactive and at which decomposition and discoloration occur are inherentin the separate polymers, these details may be determined by experimentfor the polymers that are to be used. As to the length of time that thisheat treatment should be given, the higher the temperature, the shorterthe time may be. However, it is desired that the treatment be givenuniformly.

While the heating medium may be any mems that can give a uniform heattreatment to the polymers, from a practical standpoint, steam, air, etc.are conveniently used.

(b) In this case, as good solvents, there can be cited tet'rahydrofuran,cyc-lohexanone, methyl isobutyl ketone, acetone, dioxane, etc. and asnon-solvents, water, methanol, gasoline, etc. In mixing the two, it isnecessary to insure that an intersoluble solution is made.

While the minimum solvent concentration will differ depending on thecombination of the solvent and nonsolvent selected, if the solventcontent in the solution is excessively small, the desired effectivenessin treatment cannot be obtained. For instance, in thetetrahydro'furanwater system, tetrahydrofuran must be over 10%; Theupper limit of the solvent concentration must be such that the polymerparticles. are not dissolved. For example, in case of thetetrahydrofuran-water system, the tetrahydrofuran content must be lessthan 70% by weight. However, when the solvent concentration is as largeas this, in case it is heated, the polymer particles tend to becometacky. Therefore, if the tetrahydrofuran-water system-is to be used, itis preferable that the tetrahydrofuran concentration be less than 30%Moreover, in case the solvent concentration is high, since there is theefiectiveness that the removal of the low molecular weight parts of thepolymer is effected by means of dissolving, if the ratio of the liquidto the polymers is made more than five times and the polymers aresteeped therein for a long period of hours, it is possible to make thepolymers into stable polymers that do not contain the low molecularweight parts therein.

On the other hand, if the solvent solution to be added to the 'PVC-L isto be held to the minimum required amount, generally a liquid to polymerratio of 0.1-0.4 may be used, and thus the operation is simplifiedgreatly. When performing the aforesaid treatment, if a stabilizer of PVCis mixed in the solvent solution, decomposition can be prevented duringthe heating that follows this type of solvent treatment. Although thetemperature and length of time of this type of solvent treatment has notmuch elfect on the treatment results, in general, it'is preferable thatit be over 30 minutes at an'ordinary temperature.

The heat treatment method as described in subparagraph (a), above, canbe used after the solvent treatment. and by this heating the solventcontained in the polymer is driven out.

(c) In a mixed solvent consisting of a solvent and a non-solvent ofpolyvinyl chloride to which have been added organic peroxides, inorganicperoxides and other radical initiators, vinyl chloride was polymerizedin a similar manner as usual at a temperature less than 20 C. with heat,light or other means. That the D/D-valuc varies in this case dependingupon the polymerization temperature used is as described hereinabove.The solvents of the polyvinyl chloride include in this case thegenerally known tetrahydrofuran, cyclohexanone, nitrobenzene, dioxane,methyl ethyl ketone, etc. and as the non-solvents, water, alcohols,petroleum fractions such as gasoline, aromatic hydrocarbons, etc. Vinylchloride monomer itself is also included. In combining the solvent andnon-solvent, it is preferred that they dissolved each otherhomogeneously. While the ratio of the mixture will differ with eachcombination as well as the polymerization conditions such aspolymerization temperature, etc., it is preferred that a composition beused in which only the low molecular fraction that is contained in thepolymer is dissolved when the polymer and the solvent solution come incontact with each other. For example, in case of thetetrahydrofuran-water system, a 550% by weight content of thetetrahydrofuran is desirable-the expected results not being obtainableif less than 5%, while on the other hand, if over 50%, the polymersbecome tacky and hard of handling.

Next, from the polymerized content thus obtained, the treatment liquidis separated from the polymers by means of filtering, centrifuging,separating, etc., and thereafter given heating and drying treatments atthe temperature as set forth in subparagraph (a), above. The heattreatment to be performed in this case may be by air, steam, or otherheat media. Although the heat treatment time may be short if thetreatment temperature is high, in order to avoid decomposition of thepolymer, it is preferable to add in advance a stabilizer of PVC to thepolymer.

(d) While the apparent specific gravity of the polymer with an apparentspecific gravity of less than 0.2 gr./cm. can be raised to a maximum'ofabout 0.7 gr./cm. by means of the treatment methods as described in theabove subparagraphs (a)(c), inasmuch as the apparent specific gravitythat is finally obtained differs depending upon the individual treatmentconditions, by mixing together the individual PVC-Ls thus treated or bymixing with others not so treated, it is possible to adjust the apparentspecific gravity within the range from 0.3-0.6 gr./cm. It is to beunderstood that this naturally includes also those cases where thosepolymers of various types, whose apparent specific gravities are lessthan 0.3 gr./cm. on

account of non-uniformity of their particle size, are mixed amongthemselves and the apparent specific gravity is made to be more than 0.3gr./cm.

(e) While in subparagraph (d), above, we have described the instancewhen the polymer was in all cases PVC-L, this subparagraph concerns thecase when in the above subparagraph (d) PVC-L is mixed with a polymerother than PVC-L. The operation in this case is similar to that ofsubparagraph (d), above.

Although the five methods of raising the specific apparent gravity havebeen described concretely hereinabove, inasmuch as the essence of thematter lies in adjusting the apparent specific gravity of PVC-L to fallwithin the range of 0.3-0.6 gm/emf, it is'also possible to suitablymanipulate the polymerization conditions for obtaining the PVC-L invarious ways so as to prepare the PVC-L to have an apparent specificgravity of 0.3-0.6 gr./cm. from the first, and it is to be understoodthat this naturally is also included in this invention.

(2) The method of obtaining a stable swollen slurry Before describing indetail this method, an explanation will be given of the condition of thestable swollen slurry that we are seeking for. When a powdery polymer ismixed with the solvent which does not dissolve the polymer perfectly ata certain temperature, the pattern of the changes in viscosity bypassage of time exhibited by such a mixture generally follows one of thecourses as represented by the three curves of A, B, and C in FIGURE 1.

slurry. weight-composition evenin case of a. concentrated solutionsystem of -PVC-L, whichis unstable' and tends to gelation even whenmadezinto a: perfect solution, to ob- Curve A isxthat in which thepolymerhaving absorbed practicallyallof the solvent,the whole systemexhibits a wet sand-like appearance, andithushas lost its fluidity.

Curve C is'a system in which the solvent is absorbed hardly at all bythe polymer, and in which the polymer becomes a precipitate. WhilecurveB. is a condition which is intermediate to curves A and C, it isthat in which the particles of the-polymer are restrictedly swollen bythe solventand while maintaining this swollen state, the viscosity'gofwhole systemtends to reach a state of equilibrium without the.destruction :of the swollen polymer particles and moreoverwhilemaintaining a. stateinwhich the polymers are not segregatedfromtthe solvent. It is 1 that of a slurry which shows a constantfluidity. as well as practically no changeiin its condition with. thepassage We. "shall 1 refer. to the slurry system, as represented bycurve'iB, whose viscosity reaches an equilibrium value and in which'ltheWiscosityshows small change in its condition with. the; passage of timeas the stable We found that it .waspossiblewith .thesame taina slurry.state'in which the. swelling-does not con- ,tinueyas shownincurve; B ofFIGURE 1,. and thus pos :sessesstability rand fluidity' forascomparativelydong :period of .hours. .And .since. if the variousoperations other. :than .the. dissolving vrequired. for spinning; suchas transportation, deaeration, 'mixingyetc' could bevperformed inthis'state, there was noxtnccessity .of handling the'solutionforlongwperiods' of hoursin an unstable state. There- .fore, we-t'ound.that it was yery. advantageous, since the fiber formationbyspinning could' be performed while .the solutionrwasxinaperfectlydissolvedstate.

- A few'examples ofsthe conditions will bexgiven below in order toshowwhatitypeofrpoiymers andwhat type of solventswill-ebe :used andinwhat-'mannertoattain the objective ofcproducing fibers and. also inobtaining the .slurrywhosestate israstshown in curveB of FIGURE 1.

(a) That Pvc-Lwwith an apparent sspecific gravity of 03-06 is used.

(b) Thatthc'solvent is armixed solvent inwhichat least one. ofitscomponents is ketone'with axc'arbon atoms number of 3' to 8.

,(c) Thatlpreferably a solvent; whose. surface-tension I isvgreat'isused. I

:Each of the aboveconditions will be described :in detail-below. I r (d).Thecapparent specific v:gravityof' BPVCeL can be vmadeito befrom0.3'-0.6.gr./cni. by the several methods as already.described above.

(1)1tzisn-believed .thatby a .trcatmentsuch as. this the .fine"structure of: the:.polymer becomes compactand dense andits porous.character islost, whereby the amount of thesolventzxthat permeates into.the. polymer particles when the polymer: and solvent areblended isrestrained.

The lessenthe extent of sthetreatment described in subparagraph (1) and-:the -smaller" the apparent'specificv gravity, the'stateof theslurrytproximates that of curve .Ain FIGURE 1 and the: equilibrium'stateof viscosity becomes. high. Ontheother'hand, when-the treatment isextensive and the apparent. specific .gravity becomes morethan 0.6,.thestate of the slurrywbeingsimilar to that of cu rve C of FIGURE land notexhibiting a homogeneous slurry-like state, segregation. is causedbetween form the stable slurryz possessed of fluidity. That is, it mustbe such that while at comparatively low temperatures it only manifestssolvent power to the extent that it causes restrictive swelling of thepolymer particles. At high temperatures it must possess suificientsolvent power as will completely dissolve the polymer. Although thesolvent that. .satisfies this condition may be a single one, we wereable to find many thatsatisfy the-above condition from among the mixedsolvents of two components that are obtainable'commercially withrelative case.

As suitable solvents that can achieve this objective, there canbe' givena single or a mixed solvent which contains at least as one of itscomponents aliphatic-ketones having 3 to 8 carbon atoms. Of these, inmost instances themixed. solvents are particularly'suitable forachieving theobjective. As these ketones, there can be illustratedacetone, methyl ethyl ketone, iso-propyl ketone, methyl iso-amyl ketone,ethyl iso-propyl ketone, di-iso-propyl ke- .amyl..acetate. From "thestandpoint of solvent power, theratlo-byweight of the composition of themixed solthe other component is made to be 5 80%.

those having a high boiling point is at a disadvantage tone, diacetonealcohol, mesityl oxide, phorone, isophorone, etc.

Whileany optional two of the foregoing may be mixed, in case anothercomponent is to be mixed,'as examples of such other components there canbe cited aromatic hydrocarbons, chlorinated hydrocarbons, etherderivatives of .ethyleneiglycol, and esters derived from aliphaticalcohols. ,And,.as' aromatic hydrocarbons, there can be named benzene,toluene, ethyl benzene, and xylene,'aschlorinated and hydrocarbons,dichloroeth'ane, tetrachloroethane, chlorobenzene,- asethers fromethylene glycol, dioxane, andas esters from aliphatic alcohols,ethyl-acetate and vent issuitable if one of the components is made to be95-20% of the ketone having 3 to 8 carbon 'atoms and Also since in theremoval of the solvent after fiber formation, it is preferred thattheselection be made sothat the boiling point of the mixture becomes lessthan 170 C. Furthermore,'in consideration ofthe time when the slurry isheatedand. dissolved, in case the temperature necessary for dissolvingthe polymer at the desired concentration -is far. higher than theboiling point'of the mixed solvent, by

1 thefollowing two methods it is possible to easily avoidtheboiling ofthe solvent at the time of dissolving; namely,

.eitherby suitableselection of the component other than the-ketones,whereby the boiling point is raised without change insolventpdwer or byselection as ketone com- 'ponent thatwhose molecular weight is larger,whereby the. solvent power is. increased.

(c) While wehave stipulated in the above subparagraph- (b) that thesolvent for obtaining the stable? slurry must in the first place possesssuflicient solvent "power, anotherimportant thing with regard to thesolvent 18 its surface tension. In subparagraph (b), as solvents thecyclic ethers such as trimethylene oxide, tetrahydrofuran, etc. wereomitted. This was because these are good solvents with low viscosity andmoreover whose 'interfacial tension with PVC-L is small, which even whenmaking contact with the polymers when cold, by their sudden permeationinto the polymer particles causes them to swell excessively and thuscannot form a stable slurry.

Ifmention is to be made of the relationship between the surface tensionof the solvent and the type of polymer with which it is to be mixed, itis that, generally speaking, .in-case of a solvent with low surfacetension, it is suit-f able to use a. polymer, having a high apparentspecific gravity in combination therewith. The reason for this isbecause with this type of polymer, on account of the fine structurebeing compact and dense, even though the surface tension of the solventis small, the permeation of the solvent can be restrained remarkablywell, and it is possible to avoid the sudden and excessive swelling ofthe partlcles. However, if the treatment of the polymer has'beenoverdone and the apparent specific gravity of l the polymer is more.than0.6, the fine structure of the 5' particle becomes too hard, and sinceit will no longer permit the penetration of the solvent at roomtemperature, it is not possible to prepare a stable slurry by itselfalone. Moreover, even though a stable slurry has been formed by mixingthe polymer with a solvent having a high surface tension, and anequilibrium state of viscosity has been obtained, in case this polymeris combined with a solvent having low surface tension, it does notnecessarily follow that an equilibrium state of viscosity will beobtained. Even if equilibrium is obtained, it is usual that itsequilibrium viscosity is high.

By reference to the various methods, as hereinabove described, it ispossible to obtain a stable slurry with small change in its viscosity.However, a slurry that is convenient for spinning is that which shows aviscosity of 5'-200 stokes. This is because if it is less than 5 stokes,there is the possibility that the polymer and solvent which has alreadybeen mixed will segregate. On the other hand, if the viscosity is morethan 200 stokes, because of its excessive viscosity, the handling of theslurry becomes difficult with such possibilities of the progressiveviscosity increase during its storage and periods of stagnancy as wellas difficulties of transportation.

Even after the various values with respect to the polymer and thesolvent have been decided as above, the equilibrium viscosity that isexhibited by the slurry obtained by mixing the above may be adjusted bychanging its thermal career in mixing. Therefore, by merely adjustingthe temperature, it is possible to adjust the viscosity of the slurry to20-80 stokes which is the most convenient for its handling. Since therise in temperature in this case brings about an irreversible increasein viscosity, while it is possible to raise the temperature of theslurry for the purpose of raising its viscosity, once the temperaturehas been raised, the lowering of the viscosity of the slurry is notpossible by a later lowering of the temperature. Needless to say, whilethe viscosity of the slurry varies with the mixing ratio of the polymerand the solvent, i.e. the concentration, it is limited by the fact thatit must be within the range wherein it will permit ease of operationssuch as transportation in the slurry state, and moreover can be spunwhen heated and dissolved. The suitable concentration is 20-40%. Theslurrywhich has been obtained in this manner is stable, and so long asit is kept at room temperature the swelling does not progress nor isthere a change in its viscosity. Thus, it is readily possible to removethe bubbles that have become mixed in during the preparation of theslurry either by leaving it standing or by performing slow or mildmixing, and moreover its stability can be maintained during the timerequire for carrying out the various operations such as transportation,filtering, etc.

Furthermore, by adding during the preparation of the slurry otherpolymers that are directly soluble in the solventin an amount less thanby weight with respect to the PVC-L, it is possible not only to preventa sudden changein the viscosity of the slurry but also by the spinningof blended polymers to impart to fibers properties not possessed byPVC-L.

(3) The method of dissolving the slurry.

The production on an industrial scale in a most effec- .tive manner ofthe polyvinyl chloride fibers improved in their thermal properties isachieved by carrying out the following operations with respect to thestable slurry Whose viscosity change is small, this slurry having beenobtained, as hereinabove described, by increasing the apparent specificviscosity of the PVC-L polymer and then combining the polymer with thesolvent. Namely, we found the method of spinning wherein this type ofslurry, immediately prior to the spinning, having been heated anddissolved at a temperature of 100-200 C., was made into a viscoustransparent dope, and then, if required, filtered, and immediately spunfrom a spinneret. The viscous transparent dope, as used in thisinvention, which has been obtained by heating and dissolving theaforementioned PVC-L, differs completel from the ordinary entirelydissolved solution of polymer in the fact that it tends to causephenomena such as decomposition, discoloration, etc. as a result of therise of its viscosity with the passage of time, and if the temperaturefalls, with a sudden rise in viscosity, it becomes ditficult to performthe various time-consuming operations as have been heretofore practicedsuch as storage, transportation, etc. Hence, the necessity arises inthese instances of reducing to the minimum the time required for theheating and dissolving operation as well as the time that elapsesbetween the heating and dissolving operation and the spinning operation.The temperatures at which the heating is to be performed during theheating and dissolving of polymer is determined by such as the solventpower of the solvent, the concentration of the slurry, the averagedegree of polymerization of the polymer, its D/D-value, etc. While itsuflices with a comparatively low temperature when a polymer of a lowdegree of polymerization and having a small D/D-value is dissolved to alow concentration using a solvent having a high solvent power, inproducing economically the fibers improved in their thermal properties,heating at about 100-200 C. is required. A temperature of over 200 C.not only tends to cause thermal decomposition but also makes operationsdifiicult of performing even if a stabilizer is added.

When filtration is required, while it is preferable to perform thefiltration subsequent to the heating and dissolving operations itconsideration is given to the points of pressure required for filtrationand the filtration effectiveness, it is also possible to perform thefiltration while being transported in the slurry state or the twooperations may be combined. I

To prevent the solvent from boiling when it is being extruded from thespinneret, the temperature of either the dope prior to its being spun orthat of the spinneret may be lowered. Furthermore, while it ispermissible to add a small amount of plasticizer to improve the fluidityof the solution, or a stabilizer to prevent thermal decomposition, formaintaining the quality of the product, it is best to hold this to assmall an amount as possible.

The polyvinyl chloride fibers can be obtained by spinning the thusobtained polymer solution through a spinneret using either the dryspinning or the wet spinning process. However, in this invention, thedry spinning process is the more efiicacious.

By imposing the conventional drawing operation of drawing to 2-10 timesat a temperture of -115 C. and giving a heat treatment at 70l30 C. tothe polyvinyl chloride fibers produced by using the highly crystallinevinyl chloride polymers obtained as described hereinabove, it ispossible to obtain fibers excelling in dimensional stability the fibersthat are obtained from polymers by the high temperaturepolymerizationmethod.

However, it has been found that polyvinyl chloride fibers with furtherimprovements in their dimensional stability could be obtained byperforming the drawing method and heat treatment method as describedbelow.

While polyvinyl chloride fibers are imparted great tenacity with respectto stretching by being imposed the conventional hot drawing of 2-10times at a temperature of 95-115 C., in accordance with our studies, wefound that it was possible to obtain polyvinyl chloride fibers excellingin thermal as well as mechanical properties even though the drawingratio during hot drawing was less than 2 times. What we found was thatit was sufficient if the product of the drafting ratio at spinning andthe drawing ratio at hot drawing became more than 2.0. This means thatit is possible to obtain serviceable fibers even if drafting at spinningis only imposed and hot drawing is not performed. However, from thestandpoint of spinning technique, there is a limit to the increasepossible in this drafting ratio at spinning, it being difiicult toincrease this ratio too much. By giving heat treatment .13 after drawingat a temperature of 701 70 C. to the fibers obtained from PVC-L, fiberswith still greater improvementsin their.dimcnsional stability can beobtained.

In the conventional polyvinyl chloride fibers, due to i of softening.

14. ples.1% was obtained. This was thenmade the stilfness, which wasused as the criterion for indicating the state If the ratio of thestiline'ss of the two samples at 100 C. are sought from FIGUREZ, samplethe fact, that the softening temperature 'exhibitedby the No. l is morethan 5 times that of sample No. 2. Thus, polymer was low and thetenacity.at high-temperature .it has'been .shown that the hardnessof thepolyvinyl of the fibers was-exceedingly small, it was not possiblechloride fiber whose D/D-value is 1.192 is indeed .more after hot.drawing to :heat treat at constant length the than 5 times that of theconventional polyvinyl chloride .fibers at a temperature. above 130C..since breaks in the vfiber. v g v fiberswoirld occur on account ofthermal stress. I-Iowa While hereinabove we have described the instancewhen w I ever, in.. accordance with the fibers: of this invention, itpure polyvinyl chloride is used, in this invention, of thosehasbecofnje'possibleto perform. the heat treatment atvinylfichloridepolymers polymerized at a low tempera- .above 130 C. since, as haszalreadyvbeen described hereture, those containing as a whole more than90 mol perinabove, thepolymer itself. is highly :crystalline and hascent of vinylichloride units may be used. These types a small thermalstress, and the:tenacity at high. temperaof polymers may be eitherobtained by copolymerization v ture of the fibers is greatJ Whenthe;heat-treatment is or. polymer blending, or the combination of thereof.As carried out latisuch a highvtemperature as this-not only iscomonomersin the copolymerization there can be cited it possibleto'xobtain thedesired:results in ashort time, the vinyl compoundsand theolefins thatare capable of but-alsothe results obtainedaare' great.While the time being copolymerized with vinyl chloride. .And as therequired for heat treatmentwill vary rdepending on the polymer'that canbe used in polymer blending, any polytreatmentefliects that one.expectsnormallyythe time remercapable of being dissolved in the solvent 01:polyvinyl .quired -.will' beithat time rwhich will make possible thechloride may be used: for example, there may be cited reduction of.theresidual-solvent'of the'fiberformedto an such as .polystyrene, thepolyacrylates, the polymethacryamount. less. than 0.5% lates,polyacrylonitrile, polyvinyl acetate, or the polyvinyl vDuring:thewheat:treatment, wother i heretofore known chlorideobtained by the hightemperature polymerization r ones such as heat-treatment with restrictedshrinking, heat method. v v I treatment with freeshrinlcingpandtheattreatment-with Thus, in accordance with this invention, it ispossible stretchingmay.:also."be performedvbesides" the heat xtreattoobtain on' an industrial scale fibers using as starting Wmentatrconstant' length. film/general; the combination of materials highlycrystalline vinyl chloride polymers conheattreatmentat'constantalengthandiheat treament with tainingmorethan 90 molpercent' of vinyl chlorideunits shrinking not-:only: .makes possible the 1 further raising of andmixed polymers obtained by mixing this type of vinyl theheat"treatment'temperature' but-:also =isauseful'in1 the chloridepolymerwith other polymers insuring that the improvement ofltheuproperties of :.:the* fiber. Inasmuch total vinyl chloride unitscontained in the mixture does as thermal decomposition ecannot beavoidedwhen rwheat not become less than 90 mol percent. The fibers obtainedtreatment is performed foi -1110117111311 10"rninutes' at a' 'by themethod of this invention are superior to the contempenaturei ofmore-zithan 170 .C., it is not suitable 'for ventional polyvinylchloride fibers, especially with respect the production of'fibersb ByrefeI'ence toTable IV, item to suchproperties as dimensional stabilityas well asbeseen more clearlyehow' 'great an improvement maybe tenacity,extensibility, etc. at high temperatures. obtained in'the""thermal: andmechanical :properties by :In' order to more clearly understand thepresent inventhese conditions. 40 tion, the-following specific examplesarefgiven, it being TABLE IV Properties of fibers I 4 Drawing conditionHeat setting condition" p i t S Strength. Extensi- (percent) (gm/den.)bility M (percent) Draw ratioi'ss N n 34.2 2. (i3 19.? Temperature:..C.-. 6.6-3 mins. (AWZ 12.0 2. 72 21.4 Medium: in saturated 0. -3 mins.(A) 7. 2 .2. 77 22. 5 steam. C.3m1ns. (A) 6.6 2. 69 23.1 Not drawn None11.8 0.47 57.3 Drafting ratio at spin- 130 C.-5 mins. (A) i 4. 3 0. 6127. 7

ning: 2.2. Draw ratio: 4.0- Temperature: 115C None. 35.9 2. 61 19.0Medium on {iili bffiiiltfii $3151: i323 3121 iii I Test fibers were spunby dry spinning from methyl et hyl ketone and toluene solu--- tioncontaining ZSWeight pereentot polymer (DID =1.l88 P=1l90). The draftingratio at spinning was 1.2, unlessotherwise mentioned.

SPereent shrinkage on immersing the fiber in boilingwater for 5 minutes.

@ (A)Heat set at constant length. d (B)'-Heat set-at 130 C. withrestrictive shrinking of 10%.

' In conclusion, the significant'ditr'erences between the polyvinylchloride fibers obtained in: accordance with this temperature-elevationof 1.0 C./min. under'the loads of 0.010 gr./den. and 0.030gr./den.irespectively, and from the. respective. thermal shrinkage thatwere manifestedlthereby, the load required to stretch the fibersamunderstood that the same 'aremerely intended in an illustrativesense,and the invention should not be'limited thereby, but only insofar as thesame may be limited by the appended claims.

EXAMPLE 1 To vinyl chloride monomer, 1.13 mol percent thereof oftri-n-butyl boron was added, and the mixture was polymerized at 20 C. innitrogen atmosphere with stirring. After 3 hours the polymerization wasterminated by the addition of-a mixture of cone. NH 0H aq. and methanoland the resulting polymer was separated and washed with methanol, Byair-drying the same at 50 C., a

white powdery polymer is obtained at 26.7% yield. This V 15 polymer thenwas dissolved in eyclohexanone at the concentration of 4 g./l., and thesolution showed at 30 C. an average degree of polymerization of 1240when measured by Ostwaldt viscometer.

The polymer also showed an apparent specific gravity of 0.16, and a D/Dof 1.184.

When this polymer was heat treated for 15 minutes in the steam underpressure of 110 C., the apparent specific gravity went up to 0.38.

30 parts of this heat treated polymer were mixed into a mixed solventconsisting of Zlparts of cyclohexanone and 49 parts of benzene at C.When said temperature is maintained with continuous stirring, themixture reached the equilibrium state of viscosity after 100 minutes,and a stable slurry of uniformly swollen polymer particles having aviscosity of 5 stokes was obtained.

This slurry was dissolved into dope by passing continuously through aheating tube at 145 C., and thereafter the dope having a loweredtemperature of 100 C. was spun into a hotair stream of 135 C. througha-spinneret, and after the solvent was vaporized therefrom, theresulting filamentary yarn was taken up at a winding speed of 240m-./min.

This filamentary yarn was drawn 6 times its original length in a steamunder pressure of 110" C., and then heat treated for 3 minutes, bypassing through a flycerine bath maintained at the-temperature of 145 C.

The properties of the resulting fiber were as follows:

Tenacity g den.. 3.16 Extensibility percent 26.8 Density 1 g/cm.'..1.415 Shrinkage in boiling water percent.. 8.4 The temperature at whichthermal shrinkage under the load of 0.01 g./den. becomes 10% C... 107

Further the properties of the original filamentary yarn which wasobtained by heat-melting and spinning the Extensl- Shrinkage Tanacltbillty in boiling (g./den. (percent) water (percent) Original filamentarn.-- 0. 96 83 14.2 Heatrset filament r y 1. 01 42 3. 7

EXAMPLE 2 To vinyl chloride monomer, 1 mol percent thereof of triethylboron was added to polymerize the monomer at -40 C., and after 3 hoursthe polymerization was terminated by the addition of a mixture of cone.ammoniac liquid and methanol. The resulting polymer was sep'-' arated,washed with methanol, and air-dried at 50 C. A white powdery polymerhaving an average degree of polymerization of 910, an apparent specificgravity of 0.14, and D/D of 1.248 was obtained at yield.

-To each 1 part of this polymer 0.01 part of a stabilizer and 1 part ofan aqueous solution containing by weight of tetrahydrofuran were addedand mixed well.

After being left for an hour, the mixture was heat treated for 10minutes in steam under pressure of 130 C. and dried at 45 C. A polymerhaving an apparent specific gravity of 0.44 was obtained.

On the other hand, when 0.01 part of the stabilizer and 1.5 parts of anaqueous solution containing by weight of tetrahydrofuran were added toeach 1 part of the polymer having an apparent specific gravity of 0.14,mixed well, left for minutes, heat treated for 30 minutes in steam of100 C., and dried at 45 C., a polymer having anapparent specific gravityof 0.32 was obtained.

16 The thus obtained two kinds of polymer, each having anapparentspecific'gravity of 0.44 and 0.32, respectively, were mixedtogether at a ratio of 12:18, respectively, to form a blended polymerhaving an apparent specific gravity of 0.35. Said polymer was then addedto a mixed solvent consisting of 30 parts of acetone and 40 parts oftoluene at 0 C. with continuous stirring. When the temperature of 0 C.was maintained under said continuous stirring, an equilibrium state ofthe viscosity was reached after 45 minutes, and a slurry having aviscosity of 125 stokes was formed.

This slurry was continuously dissolved into dope by passing through aheated tube at 150. C., and when the temperature of the dope wasgradually lowered to C. near the end of said tube, the dope was spuninto a hot air stream of 130 C.through a spinneret. The resultingfilamentary yarn was taken up at a winding speed of 170 m./ min.

This filamentary yarn was drawn 8 times its original lengthin aglycerine bath of C., and further heat set by passing through aglycerine bath of 155 C. for one minute. The properties of thus obtainedfiber were as follows: 1

Tenacity g/den 2.78 Extensibility "percent..- 16.4 Density (113)..-1.421 Shrinkage in boiling water ..percent 5.9 The temperature at whichthermal shrinkage under the load of 0.01 g./den. becomes 10% C 134EXAMPLE 3 The polymer obtained in Example 1, having an apparent specificgravity of 0.16, a degree of polymerization of 1240 and a D/D of 1.184,was steeped for 30 minutes in 10 times by volume of 20% aqueous solutionof tetrahydrofuran containing 1% by weight of a stabilizer at a roomtemperature. Then the polymer was filtered, heat treated for 30 minutesin steam of 100 C., and air-dried at 50 C., resulting in the formationof a polymer having an apparent specific gravity of 0.30.

Also, by similarly steeping the polymer of Example 1, heat treating thesame in steam under pressure of C. for 10 minutes followed by air-dryingat 80 C. for 2 hours, a polymer of an apparent specific gravity of 0.49was obtained.

Each 15 parts of the above polymers of apparent specific gravities of0.30 and 0.49, respectively, were mixed well, and the resulting blendedpolymer of an apparent specific gravity 0.39 was added to a mixedsolvent consisting of 35 parts of methyl ethyl ketone and 35 parts ofbenzene in a mixing vessel at 0 C. with continuous stirring. When saidtemperature was maintained under said continuous stirring, a stableslurry of uniformly swollen polymer particles having a viscosity of 52stokes was obtained.

This slurry was continuously sent into a heated tube at 145 C. by a gearpump, and dissolved therein. When the temperature of the dope waslowered to 100 C., the dope was spun through a spinneret into a spinningcell through which a hot air stream of 135 C. was constantly passing.After the solvent was vaporized, the produced filamentary yarn was takenup at a winding speed of 240 m./min.

This yarn was drawn 6 times its original length in steam under pressureof 110 C., and then heat treated for 3 minutes by passing through aglycerine bath of C.

The properties of the obtained fiber were as follows:

EXAMPLE 4 Two hundred parts of vinyl chloride were dissolved into 280parts of methanol, and polymerized for 18 hours under the irradiation of300 W. high pressuremercury lamp at -S C., with the addition of 1molpercent based on the monomer, of di-tert-butyl peroxide andtriethanolamine. The resulting polymer was separated, washed'withmethanol, and dried at 50 C. A white powdery polymer Shaving an average"polymerizationdegreeof 2150, an apparentspecific gravity of 0.19 and'aD/D of 1.145'was obtained at,34.5% yield. i

'When thispolymer was heat treated steam under pressure of 120Cthe'products apparent specific gravity became 0.32, and when heattreated for 15 minutes-in steam-under pressure of 130 C., the resultingpolymer'had an apparent specific gravity of 0.43.

By mixing up each 101parts of these three polymers for 15 minutes inhaving each dilferent' apparent specific gravity, a blended polymer ofapparent specific,gravity0.39 was obtained.

parts of this blended polymer were then added to a mixed solventcooled'below.0 C., .consisti'ng of 28 parts of cyclohexanone containing03 part of a stabilizer, and 42 parts of benzene with continuousstirring, while maintaining the temperature of the solution at 0 C.After' 60 minutes an equilibrium state" of the viscosity was reached,and astable slurry ofuniform composition'having a viscosity of 6 stokeswas obtained. 3

This slurry was continuouslysent into a tubeiwhich uwas-heated to 158C.-by agear pump to. be dissolved into dope, and the temperatureof-saiddope was lowered to 110 C. in said tube. "Thereafter the dope was spunthrough a'spinneret into a spinning .cell through which a hot airstreamLot 140C. was :constantly passing. The

resulting.filamentaryyarnwas taken up. at a winding speed .of 120m./min.

This filamentary yarn was drawni5 times its original lengthinhotwaterof96 C.,.and.then heat.treated for 5 minutes by passing through.an ethylene glycol bath maintained at 135 C.

The following Examples "5 .to .10 show recipes for the Q production ofstable slurries,by.subjecting a-polymer to various treatments.TheQslurries obtained in accordance with these recipes are suitable forwet-spinning aswell .as dry-spinning, providing fibers ofzexcellentthermal properties v EmMPL-E '5 By mixing '11.2'parts of the polymer ofExample l'having an apparent'specificgravity of 0.16 and 168 parts ofthe polymer of Example 3 having an apparent specific gravity of 0.49,,ablended polymer of an apparent specific gravity of 0.34 was obtained.

This polymer was added to'a mixed solvent.v consisting of 36.0 parts ofmethylethylketone containing 0.14 parts of a stabilizer and 36.0 partsof toluene at 0C., which temperature was maintained for 45 minutes tillthe equilibrium stateof the viscosity wasreached, and a stable slurryhavinga viscosity of 5 1 stokes was obtained.

EXAMPLE 6 'By mixing each 13 parts of the polymers of the Example 4 eachhaving an apparent specific gravity of 0.19 and 0.43, a blended polymerof an apparent specific gravity 0.35 was obtained. This polymer wasadded to a mixed solvent consisting of 37 parts of methyl ethyl ketonecontaining 0.1 part of a stabilizer and 37parts of xylene at 0 C., whichtemperature was maintained for minutes .till

an equilibrium state of viscosity was reached and a stable.

slurry having a viscosity of 32 stokes was obtained.

EXAMPLE 7 13.6 parts of .a polymer having an apparent specific gravityof. 0.35, obtained by heat treating the polymer of Example 1 havingan'apparent specific gravity of 0.16 for 10 minutes instear'nunderpressure of 120 C., was mixed with 20.4 parts of thepolym-er of- Example3 having an apparent specific gravity of 0.49. A blended polymer of anapparent specific gravity 0.42 was obtained.

. This polymer was added to a mixed solvent consisting of 30 parts ofmethyl ethyl ketone containing 0.2 part of a stabilizer and 36 parts ofbenzene at 0 C. and maintained under the same temperature tOr'35minutes, 'till the equilibrium state, of viscosity was reached and astable slurry having a viscosity of 106 stokes was obtained.

EXAMPLE 8 15 parts of the polymer of Example 2 having an apparentspecific gravity of 0.44 and 15 parts of a polymer of an apparentspecific gravity 0.30, obtained by heat treating the polymer of Example2 having an apparent specific gravity of 0.14 for 10 minutes in steamunder pressure'of 120 C., were mixed together and a blended polymer of.an apparent specific gravity 0.36 was obtained.

'This polymer was added to a mixedv solvent, consisting of 35 parts of{methyl isobutyl ketorie"-containing0L2 part of a stabilizer ant-1.35parts ofbenzene at 0 C. When said temperature was maintained for 50minutes, the equilibrium state-of viscosity was reached and a stableslurry having a viscosity of 72 stokes was obtained.

EXAMPLE 9 30. parts of the polymer obtained in Example 2 having an.apparentspecific gravity of 0.44 were added to a mixed solventconsisting of 28 parts of methyl isobutyl ketone containing 0.3 part ofa stabilizer and 42 parts of toluene at 0 C. .Said temperature wasmaintained fori50 minutes till the equilibrium state of viscpsity'wasreached and :a stable slurry having a viscosity of 9 stokes wasobtained.

, 'EXAMPLE 10 .A polymer, having an apparent specific gravityof 0.31

was obtained by heat treating the polymer obtained in Example 4, havingan apparent specific gravity ofv 0.19, for 5 minutes in steam of 110 C.30 parts of this polymer were added to 70 parts of cyclohexanonecontaining 0.3 part'ot a stabilizer at 0 C. Said temperature wasmaintained for 60 minutes till the equilibrium state of viscosity wasreached, and a stable slurry having a viscosity of 11 stokes wasobtained.

In the following Examples 11 to 14, recipes for obtaining stableslurries by adding solvents at the time of p0lymerization are shown.These slurries are suitable for wetspinnirig as well as dry-spinning,providing fibers of improved thermal properties.

EXAMPLE 11 for 4 hours, the polymerization was terminated by addingamixt'ure of ammonia and methanol. The resulted polymer was separated,washed with methanol solution containing 20% by weight tetrahydrofuran,and dried at C. A white powdery polymer having an apparent specificgravity of 0.32, and an average polymerization degree of 1190 wasobtained at 28% yield.

This polymer was again thoroughly washed with methanol and measured withan infrared absorption spectrum, the value of its D/D being 1.173.

By mixing this polymer with a mixed solvent in ac- 19 cordance with thefollowing recipe, a stable slurry was obtained.

p EXAMPLE 12 An autoclave provided with a stirrer was charged with 400parts of 20% tetrahydrofuran aqueous solution, 20 parts of 10% sodiumlaurylsulfate aqueous solution, and 4.0 parts of'tri-n-butyl boron,which were mixed together. 120 parts of vinyl chloride were addedthereto under pressure, and reacted therewith at C. for 8 hours withstirring. The resulted polymer was separated, washed with 20%tetrahydrofuran aqueous solution, and dried at 95 C. The thus obtainedpolymer had an apparent specific gravity of 0.38, an averagepolymerization degree of 1320, and a D/D of 1.108, with 48% yield.

0.14 part of this polymer was mixed with 0.14 part of a polymer havingan apparent specific gravity of 0.57, obtained by heat treating thefirst polymer for 20 minutes in steam under pressure of 110 C., and ablended polymer of an apparent specific gravity 0.47 was obtained.

This polymer formed a stable slurry by the following recipe:

Methyl ketone parts 36 Toluene do Time required before the equilibriumstate was reached min 35 Viscosity at the time of equilibrium stokes 51Temperature C 0 EXAMPLE 13 v To the mixture of 100 parts of vinylchloride and parts of cyclohexanone, 0.3 part of tri-n-butyl boron wasadded in nitrogen current at -30 C., and the resulting A stable slurrywas formed from this polymer by the following recipe: r

The polymer having an apparent specific gravity of 0.47 par-ts.... 15 Apolymer having an apparent specific gravity of 0.32 do 15 v(Theirblended polymer having an apparent specific gravity of 0.39.) Acetone31.5 Toluene do- 38.5 Stabilizer do--- 0.3 The time required before theequilibrium state of viscosity was reached "min--- 40 Viscosity at thetime or equilibrium stokes 115 Temperature C +5 EXAMPLE 15 18 parts ofthe polymer of Example 14 having an apparent specific gravity of 0.47were mixed with 12' parts of the polymer of Example 3 having an apparentspecific gravity of 0.30, and ablended polymer of an apparent specificgracity 0.38 was obtained. This polymer is mixed into a'solvent mixtureconsisting of 28 parts of methyl ethyl ketone containing 0.3 part of astabilizer and 42 parts of ethyl acetate at 0 C. When this temperaturewas maintained for 30 minutes, the equilibrium state of viscosity wasreached and a stable slurry having a viscosity of 40 stokes wasobtained.

EXAMPLE 1e 9 parts of the polymer of Example 11 having an apparentspecific gravity of 0.32 were mixed with 18 parts of the polymer ofExample 3 having an apparent specific gravity of 0.49. A polymer havingan apparent specific gravity 0.42 was obtained.

This'polymcr was mixed into a mixed solvent consisting of 33 parts ofacetone containing 0.15 part of a polymerization was continued for 5hours under stirring.

The thus obtained polymer was divided into two parts and each part washeated to 80 C. and 100, 0., respectively, both parts yielding slightlyyellowish polymers of an average polymerization degree 1650. Theapparent specific gravity of the former-was 0.49, and that of thelatterwith higher heating temperature, 0.56.

A stable slurry was obtained from these polymers by the followingrecipe:

To the mixture of 150 parts of vinyl chloride and 5 parts oftetrahydrofuran, 1.2 parts of triethyl boron was added in nitrogenatmosphere at -"0 C., and reacted therewith with continuous stirring for6 hours. After the polymerizing reaction was terminated by the additionof a mixed solution consisting of 5 parts of tetrahydrofuran and 2.5parts of cone. ammonia, the vaporized monomer was recovered. The polymerin the polymerization vessel was then dried while said vessel was heatedto 85 C. and dried air was passed through the same. A polymer having aD/D of 1.187, an apparent specific gravity of 0.47 and an averagepolymerization degree of 1050 was obtained at 24% yield.

Polymer of an apparent specific 0.49 ..-parts 16 Polymer of an apparentspecific gravity 0.56 do 16 (Their blended polymer having an apparentspecific gravity of 0.52.) Cyclohexanone do.. 34 Toluene do 34Stabilizer do.. 0.35 Time required before the equilibrium of viscositywas reached min..-.. 50 Viscosity at the time of equilibrium stokes 9Temperature C 0 EXAMPLE 14 stabilizer and 40 parts of benzene at 0 C.This temperature was maintained for 55 minutes till the equilibriumstate of viscosity was reached and a stable slurry having a viscosity of55 stokes was obtained.

EXAMPLE 17 One part of vinyl chloride monomer and 0.05 part ofacrylamide monomer were dissolved in 3 par-ts of methanol at 0 C. After0.02 part of benzoyl peroxide was added thereto, the solution waspolymerized under the irradiation of ultraviolet light by a highpressure mercury lamp for 16 hours. A polymer having an averagepolymerization degree of 1500, an apparent specific gravity of 0.15, anda D/D of 1.114 was obtained at 28% yield.

To each 1 part of this polymer, 0.01 part of a stabilizer and 0.5 partof 20% by weight tetrahydrofuran aqueous solution were added, mixedwell, left for 30 minutes, heat treated for 20 minutes in steam of C.,and thereafter dried at 50. C. A polymer having an apparent specificgravity of 0.48 was obtained.

A stable slurry was formed from this polymer by the following recipe:

Polymer of apparent specific gravity 0.15 parts Polymer of apparentspecific gravity 0.48 do (Their blended polymer having an apparentspecific gravity of 0.34.)

The thus obtained slurry was spun in a similar manner as in Example 3,and the resulting filamentary yarn was drawn 4 times its length on a hotplate, thereafter heat set in a hot air of C. for 2 minutes with 5%thermal Tenacity g./den

21 shrinkage. The properties ofthus treated fiber were as follows:

' Extensibility percent 21.6

Density (di g./cm. 1.401

Shrinkage in-boiling water -percent. 8.3 The temperature at whichthermal shrinkage under 4 the load of 0.0l g./d. becomes l%.. C-..-..118

, I EXAMPLE 1s I An example of obtaining a stable slurry by mixingpolymer ro'ther than polyvinyl chloride is given hereinbelow.

A stable slurry was obtained according to the following recipe:

The polymer obtained in Example 3, having an ap- The thus obtainedslurry wasspun in accordancewith.

the method of Example 3, and the resulting filamentary yarn was drawn 6times its original .length in boiling water, and thereafter heat treatedin steam under 'pres sure of 130 C. for 6'minutes.

The properties 'otthis fiber were as follows:

Tenacity g den 2.96 Extensibility "percent-.. 21.5 Density g /cm. 1.408Shrinkage inboilingwater "percent" 9.3 The "temperature at whichthermalshrinkage under the load of 0.01 g./den. becomes l0% .C 116 Sinceit is apparent that many changes and modificationscanbe made in theabove-described details without" departing from "the nature and spiritof ,the'invention, it is to be understood that the invention is not tobe limited thereto except'a's set forth-in-the appended claims.

What is claimed is:

1. A method of producing polyvinyl chloride fibers, wherein'th'ere isemployedas a startingmateriala polyvinyl chloride polymer containing atleast'90'mol percent ofvinyl chloride, "said polyvinylchloride polymerhaving a D1426/D1434 value of infrared absorption, as defined, of"1.08to 1.27, a polymerizationdegree of between 500 and 2500, and .anapparent specific gravity, of lessthan 0.2 g./cm. said polyvinylchloride being-obtained by polymerizinfg vinyl chloride at a lowtemperature-ranging from 20 C. to -;50' C., which method comprisesheating said polyvinyl chloride'at a temperature above the softeningtemperature at which the thermalmotion ofthe molecules become activewherebystabilization of the fine structure OCCUISyb ut below thedecomposition a D1426/Dl434 value of infrared. absorption, as defined,of 1.08 to 1.27, a polymerization degree of between 500 and .2500, andan apparent specific gravity of less than 0.2 g./cm. said polyvinylchloride being obtained by polymerizing vinyl chloride at a lowtemperature ranging ,from 20 C. to -50 C., which method comprisestreat-- ing said polyvinyl chloride in a mixture of a good solventtherefor and a non-solvent therefor over a period of time sufficient toabsorb a small quantity of said solvent mixture, and thereafter heatingsaid polyvinyl chloride at a temperature above the softening temperatureat which the thermal motion of the molecules become active wherebystabilization of the fine structure occurs, but below the decompositiontemperature of said polymer, thereby increasing the apparent specificgravity of the polyvinyl chloride to 0.3 g./cm. to 0.6 g./cm. mixingparticles of said heat-treated polyvinyl chloride polymer with a solventtherefor, thereby swelling the particles and forming a fluid, stable,swollen mixture with small change in the viscosity thereof, heating theswollen mixture thereby providing a uniform solution of said swollenmixture, and finally extruding the solution.

3, A method according to claim 1 wherein in the prep- 7 aration of saidpolyvinyl chloride a small quantity of 501- vent is added to thepolymerization system in advance,

thereby causing the polyvinyl chloride produced to absorb the smallquantity of the solvent prior to the separation of the polyvinylchloride.

4.'A method in-accordance with claim 2 wherein a ketone having 3 to 8carbon atoms is used as the solvent. 5. A methodin accordance with claim2 wherein a mixed solution obtained by mixing 95 to 20% by weight of aketone having 3 to 8 carbon atoms and 5 to 80% by weight of a compoundselected from the group consisting of aromatic hydrocarbons, chlorinatedhydrocarbons,

ether derivatives of ethylene glycohand esters derived from aliphaticalcohols is used as the solvent.

6. A methodin accordance with claim 1 wherein the polymer is mixed withthe solvent at a ratio as will give the resulting solution aconcentration of 20 percent by weight to 40 percent by weight of thepolymer, so that the particles of the polymer are swollen to form astable swollen mixture having a viscosity ranging from to 200 stokes,more preferably from 20 to 80 stokes with small change in'its viscosityin the passage of time.

7. A method in accordance with claim 2, wherein the polymer ,is mixedwith the solvent at a ratio as will give temperature-of saidpolymer,therebyincreasing the apthe resulting solution a concentrationof 20 percent by weight to 40 percent by weight of the polymer, so thatthe particles of the polymer are swollen to form a stable swollenmixture having a viscosity ranging from 50 to 200 stokes, morepreferably from 20 to stokes with small .change in its viscosity in thepassage of time.

8. A method in accordance with claim 1 wherein a ketone having 3 toS'carbon atoms is used as the solvent.

y 9. A methodin accordance with claim 1 wherein a mixed solutionobtained by mixing to 20% by weight of a ketone having 3 to 8 carbonatoms and 5 to 80% by weight of a compound selected from the groupconsistingiof aromatichydrocarbons, chlorinated hydrocarbons, etherderivatives of ethylene glycol, and esters derived from aliphaticalcohols is used as the solvent.

References Cited by the Examiner UNITED STATES PATENTS 2,481,294 9/49Corbiere et a1. 260-32.8

2,517,356 8/50 Sale 260-328 2,712,490 7/55 Stuchlik 18-54 FOREIGNPATENTS 569,632 6/59 Belgium.

MORRIS LIEBMAN, Primary Examiner.

MICHAEL V. BRINDISI, WILLIAM J. STEPHENSON,

LEON J. BERCOVITZ, Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,183,201 May 11, 1965 Jiro Shimeha et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 22, lines 43 and S0, for "50 to 200", each occurrence, read 5 to200 Signed and sealed this 21st day of December 1965.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents

1. A METHOD OF PRODUCING POLYVINYL CHLORIDE FIBERS, WHEREIN THERE ISEMPLOYED AS A STARTING MATERIAL A POLYVINYL CHLORIDE POLYMER CONTAININGAT LEAST 90 MOL PERCENT OF VINYL CHLORIDE, SAID POLYVINYL CHLORIDEPOLYMER HAVING A D1426/D1434 VALUE OF INFRARED ABSORPTION, AS DEFINED,OF 1.08 TO 1.27, A POLYMERIZATION DEGREE OF BETWEEN 500 AND 2500, AND ANAPPARENT SPECIFIC GRAVITY OF LESS THAN 0.2G./CM.3, SAID POLYVINYLCHLORIDE BEING OBTAINED BY POLYMERIZING VINYL CHORIDE AT A LOWTEMERATURE RANGING FROM 20*C. TO -50*C., WHICH METHOD COMPRISES HEATINGSAID POLYVINYL CHLORIDE AT A TEMPERTURE ABOVE THE SOFTENING TEMPERATUREAT WHICH THE THERMAL MOTION OF THE MOLECULES BECOME ACTIVE WHEREBYSTABILIZATION OF THE FINE STRUCTURE OCCURS, BUT BELOW THE DECOMPOSITIONTEMPERATURE OF SAID POLYMER, THEREBY INCREASING THE APPARENT SPECIFICGRAVITY OF THE POLYVINYL CHLORIDE TO 0.3G./CM.3 TO 0.6G./CM.3, MIXINGPARTICLES OF SAID HEATTREATED POLYVINYL CHLORIDE POLYMER WITH A SOLVENTTHEREFOR, THEREBY SWELLING THE PARTICLES AND FORMING A FLUID, STABLE,SWOLLEN MIXTURE WITH SMALL CHANGE IN THE VISCOSITY THEREOF, HEATING THESWOLLEN MIXTURE THEREBY PROVIDING A UNIFORM SOLUTION OF SAID SWOLLENMIXTURE, AND FINALLY EXTRUDING THE SOLUTION.